However, the PSNI has not matched the palm print to 64-year-old Murphy who lives in Ravensdale, Co Louth.

Rather, they are linking it to another suspect from South Armagh whom they questioned in connection with the Kingsmills atrocity last month.

The 59-year-old South Armagh man was arrested on suspicion of murder and attempted murder.

He was released pending a report to the Public Prosecution Service.

The Irish News last night defended its story saying that it had "clear information" linking Colm Murphy to Kingsmills and stating that he had been arrested by police on numerous occasions over the past 30 years.

While it is not disputed that the high-profile republican has for many years been suspected in security circles of involvement in the atrocity - which he denies - the palm-print on the van is not his.

Relatives of the Kingsmills families will today meet detectives in Armagh to discuss the police investigation and the palm print.

"Jean Lemmon is 93 years of age. Bea Worton is 89. May Quinn is 82. These women have suffered for 40 years and they deserve honest answers.

"We appreciated the police's clarity last week that they had matched the palm print to the South Armagh republican.

"We are hoping for more answers in this meeting with detectives. We want to know why it took so long to match the print," he added.

A barrister for the PSNI said in court last week that police believed the palm print found on the getaway vehicle used in the 1976 massacre of 10 Protestant workers belongs to the South Armagh republican whose name is known to the Belfast Telegraph.

Confirmation of his identity came after a lawyer acting for the families of those killed issued a plea for clarity on his arrest in Belfast Coroner's Court.

Barrister Peter Coll, representing the PSNI, said: "The person arrested is the person that police believe is the palm print."

Mr Coll continued: "I can confirm that on August 5 detectives from the PSNI's legacy investigation branch investigating Kingsmills arrested a 59-year-old man on suspicion of murder and attempted murder.

"He was arrested and questioned on the palm print that there have been some discussions about in the past.

"He was released on August 6 pending a report to the PPS. The matter rests with the PPS at the minute."

A staunch Sinn Fein supporter, the 59-year-old was one of the most senior members of the Provisional IRA's South Armagh Brigade, although he has no public profile outside his own local area.

As one of Thomas 'Slab' Murphy's most trusted operators, he was heavily involved in smuggling.

He comes from a staunchly republican family, and has been jailed for short periods outside Northern Ireland for IRA-related offences.

In response to a Belfast Telegraph query about the Irish News report claiming that the Kingsmills van palm print belonged to Colm Murphy, a spokesman for the newspaper defended the story.

He said: "We had clear information linking Colm Murphy to the investigation into the Kingsmills massacre in our coverage of June 3.

"In a High Court hearing on June 6 over a failed attempt by the Chief Constable to seek an injunction against The Irish News, police made no attempt to dispute the accuracy of our article.

"Mr Murphy has accepted that he was questioned in 1976 over the murders and in his own words has since been arrested by police on '30-plus' occasions.

"A 2011 report by the PSNI's Historical Investigation Team also effectively named Mr Murphy as the chief suspect, although he has consistently denied involvement.

"We note the evidence given to the Kingsmills inquest earlier this month about the arrest of a 59-year-old man said to be connected to a palm print found on a van used in the murders, and we further note that the individual in question was subsequently released without charge," he added.